Metering valve and method of making same



May 23, 1961 VEE c. TSIEN ET AL 2,985,566

METERING VALVE AND METHOD OF MAKING SAME Filed April 5, 1957 IN V EN T0115 VEE 0. TS] EN BY CHARLES H. BOMMERSCHEIM METERING VALVE AND IVIETHOD OF MAKING SAME Vee C. Tsien and Charles H. Bommerscheim, Kalamazoo,

Mich., assignors, by mesne assignments, to Pneumo- Dynamics Corporation, Cleveland, Ohio, a corporation of Delaware Filed Apr. 5, 1957, Ser. No. 650,965

3 Claims. (Cl. 204-35) This invention relates generally to valves and more I particularly to a new and improved metering valve having an anodized surface coating and the method for making the valve.

The use of aluminum, aluminum alloys or similar light weight materials as the spool of a spool type metering valve has been limited because such materials do not provide sufiicient wear and erosion resistance. Generally speaking, metallic electroplating on such aluminum spool valves tends to improve these characteristics, but still does not provide a completely satisfactory spool structure. A hard anodized coating produces very desirable wear and erosion resistance and has been used as a coating on certain types of valve structures. However, ithas never been very successful on precision metering valves which require very sharp edges to accurately meter fluid. This is due to the fact that the coat ing-produced by hard anodizing is the opposite of electroplating in that the reaction proceeds inwardly from the surface of the coating while in electroplating the reaction proceeds outwardly from the surface of the coating; Therefore, in anodizing as the coating is formed the specific volume increases and growth occurs. This does not cause appreciable difiiculty when anodizing a flat surface because the initially formed surface merely moves as a sheet away from the base metal as the reaction increases. the thickness of the underlying portion. However, at the corners the initial coating cannot expand in three directions and breaks and voids occur at such corners. On the contrary in electroplating the amount of material deposited as a coating is determined by the electrical current density. Because the current tends to concentrate at external corners, there is a tendency of electroplating to produce a head or thicker plating at these corners. This only introduces a minor problem since it is possible to lap off the excessive plating metal. This invention is directed to a method for producing a hard anodized coating on elements with sharp corners, such as valves, suitable for use in metering fluids and the valve structure produced according to this method.

The particular method and apparatus for forming the coating forms no part of this invention. Therefore, when the terms hard anodizing or anodizing are used herein, they refer to the oxide coating that is formed on aluminum or aluminum alloys or similar materials when placed in a bath containing acids such as oxalic acid or sulfuric acid while passing electrical current through the piece when the piece is the anode. The coating or film thus formed is basically aluminum oxide produced by electrochemical oxidation of the metal surface and is integrally bonded to the base metal.

It is .an importantobject of this invention to provide a metering valve having a sharp metering edge wherein the surfaces of the valve and edge are covered by a hard anodized coating.

It is another important object of this invention to pro- States Patent 2 vide a method of forming anodized valves or the like having sharp edges.

It is still another important object of this invention to provide a method of producing an anodized valve or the like having a sharp edge which includes the steps of forming a base metal piece with a blunt edge, producing a hard anodized coating on the base metal which extends over the blunt edge and thereafter removing a portion of the coating until a sharp edge is provided.

Further objects and advantages will appear from the fololwing description and drawings, wherein:

Figure 1 is a schematic illustration of a metering spool valve of the type which can be manufactured according to this invention;

Figures 2 to 4 show the progressive steps in forming a hard anodized coated valve plunger with a sharp edge according to one embodiment of this invention; .and,

Figures 5 to 7 show the progressive steps in forming a hard anodized coated sharp edged valve plunger according to a second embodiment of this invention.

Referring to the drawing, a normal spool valve used to control the operation of a fluid motor includes a sleeve 10 formed with a cylinder bore 11 into which a spool 12 projects. The sleeve 10 is formed with an inlet port 13 adapted to be connected to a source of fluid under pressure, two spaced outlet ports 14 and 16 adapted to be connected to a reservoir return and control ports 17 and 18. The spool 12 is'provided with a central land 19 normally closing the inlet port 13 and axially spaced lands 21 and 22 normally closing the outlet ports 14 and 16 respectively. When the spool 12 is in the neutral position shown, all the ports in the spool are isolated from each other and there is no flow through the valve. When the spool is shifted to the right, the inlet port 13 is brought into communication with the control port 17 and the control port 18 is brought into communication with the outlet port 16. Conversely, movementiof the spool to the left produces the opposite fluid connections. When such a spool valve is used to control a fluid motor such as the type including a piston and cylinder, the two control ports 17 and 18 would be connected to the opposite ends of the cylinder of such a mechanism. When accurate control is desired, it is necessary to provide sharp edges 23 on all of the lands so that accurate metering of the flow of fluid through the ports will be achieved. By utilizing the procedures according to this invention it is possible to produce a hard anodized coating on an aluminum spool 12 and still maintain the precision sharp edges required for accurate metering. Although aluminum is used as an illustration of the metal normally contemplated, it should be understood that this invention would apply equally well to any base metal which can be hard anodized to improve surface characteristics.

The methods of forming a sharp edged hard anodized valve according to this invention are based on the steps of forming the blank or base material with a blunt edge on which a hard anodized coating can be formed. After this is done a portion of the coating is removed until a sharp edge remains. In the two embodiments shown, two different types of blunt edges are used to illustrate the invention. It should be understood, however, that these two embodiments are merely illustrative and that other shapes and proportions may be used so long as they fall within the scope of the invention.

Reference should now be made to Figures 2 through 4 which illustrate the steps of one method of forming a hard anodized coating on the spool 12. The uncoated spool is first machined to the desired shape and dimen be described in detail in the following description. The blank spool 12 is then placed in an anodizing bath and a hard anodized coating 24 is formed on its surface. During the coating, some of thebase metal is combined to form the oxide anodized coating so the surface 'between the coating and the base metal 27 is. inwardly spaced from the original surface of the spool. It has been found in actual practice that a piece tends to grow by an amount equal to approximately =one=half the thickness of the coating which is illustrated by the location of the line 26 in Figure 3 which indicates the original surface of the piece and extends along the mid-point of the coating. It should be noted that the coating forms around the radius although it would not have formed if a sharp edge were present on the'base metal. It is desirable to utilize as large a radius as possible for any given thickness of coating since the quality of the coating around the corner is improved as the radius increases.

After the piece has been coated, a portion of the coating is lapped away to form finished surfaces 31 and 32 intersecting at the sharp edge 23 shownin Figure 4. The dotted line 28 in Figure 4 shows the original profile of the coating. The zone between the line 28 and the finished surfaces 31 and 32 illustrates the amount of coating which has been removed by the lapping process. Sufi'icient coating must be deposited on the piece so that the finished corner 23 is within the zone of the coating. Also the various proportions must be arranged so that a sufiicient thickness of anodized coating remains to provide a finished anodized surface 29 covering the base metal. This remaining coating, although much thinner than the initial coating deposited, provides sufiicient wear and erosion resistance so that the valve'will have a long, trouble-free service'life.

tIIl determining the dimension of the radius (R) the following formula may be used which is based on the assumption that the initial coating will extend equally in both directions from the location of the original surface of the base metal.

In the formula, R is the original radius (R) formed on the base metal; y is the thickness of the deposited coating, and x is the thickness of the final coating after the lapping operation. If the radius is determined on the basis of the formula, the finished corner 23 will'be within the zone of the original coating. An inspection of the formula will show that R can be larger if the thickness of, the original coating is increased but must be smaller if the thickness of the finished coating after lapping is increased. It is, therefore, desirable to use a relatively thin finished lapping thickness for the coating because it is desirable ot use as large a radius (R) as possible for any given coating thickness. It has been found in actual tests, that a satisfactory valve is produced if the radius (R) of the valve is approximately nine thousandths of an inch and the initial coating is approximately five thousandths of an inch wherein the finished thickness of the coating after lapping is approxi mately one and one half thousandths of an inch.

In the embodiments shown in Figures 5 through 7 a chamfer is used to form the blunt edge. The initial blank of the spool 12 is formed'with a chamfer 36 which extends diagonally between the perpendicular surfaces 37. After the blank with the chamfer' 36 is formed it is hard anodized to provide a coating'38 as shown in Figure 6. Because there is a corner at the intersection between the chamfer 36 and the surfaces 37, there will be flaws 39 between the portion of the coating formed on the surfaces 37 and the portion of the coating formed on the chamfer 36. However, since .the

chamfer 36 is substantially flat, a good coating, as shown at 41, will be provided along the chamfer. Here again the location of the original surface as shown by the dotted line 42 extends along the mid-point of the coating.

In order to form the final finished edge, a portion of the coating is removed "as shown in Figure 7 until a sharp edge 23 is formed. The various proportions should be arranged so that'the corner '23 will'belocated within the original zone of the coating 41. The flaws 39 still exist, however, they are displaced. from the sharp metering edge 23 and do 'noteifect theaccurate metering of the valve. 'In both ofthe embodiments the blank is originally formed with a blunt edge over whichan anodized coating is formed. The sharp edge is then produced by removing a portion of the coating.

Although the preferred embodiments of this invention are illustrated, itwill be realized that various modifications of the structural details may be made without departing from the mode of operation and the essence of the invention. Therefore, except insofar as they are claimed in the appended claims, structural details may be varied widely without modifying the mode of operation. Accordingly, the appended claims and not'the aforesaid detailed descriptions are determinative ofthe scope of the invention.

We claim: 7 V

1. A method of forming a hard anodize coated valve with a sharp metering edge comprising, forminga'blank of metal with first and second surfaces the projections of which will-intersect, a third surface connecting said first and second surfaces and spaced inwardly from the projected intersection of said first and second surfaces, forming an adherent hard anodized coating on said first, second and third surfaces and thereafter removing a portion of said heating from said first and second surfaces until a sharp edge is formed by the coating upon said third surface at the intersection of the planes of the coatings on said first and second surfaces.

2. A method of forming avhard anodize coated valve with a sharp metering edge comprising, forming a blank ofmetal with first and second surfaces the projections of which will intersect, and a convex rounded third-surface connecting said first and second surfaces and spaced inwardly from the projected intersection of said first and second. surfaces, forming an adherent hard anodized coating on said first, second and third surfaces and thereafter removing a portion of said coating from saidfirst and second surfaces until a sharp edge is'formed by the coating upon said third surface at the intersection of the planes of the coatingson said first and second surfaces.

3. A method of forming a hard'anodize coated valve with a sharp metering edge'comprising, forming a blank of metal with first and second surfaces the projections of which will intersect, and a ohamfer edge third surface connectingsaid first and second surfaces and'spaced inwardly from the projected intersectionof said-first and second surfaces, forming an adherent hard anodized coating on said first, second and third surfaces and thereafter removing a portion of said coating from said first and second surfaces until a sharp edge is formed by the coating upon said third surface at the intersection of the planesof the coatings on said first. and second surfaces. 7 7

References Cited in the file of this patent UNITED STATES PATENTS 2,408,790 Mack Oct. 8, 1946 2,501,616 iRobinson ..Mar. 21, 1950 2,519,488 Mack Aug. 22, 1950 2,695,628 Wheildon Nov; 30, 1954 2,860,018 Doperalski etal. Nov. 11, 1958 

1. A METHOD OF FORMING A HARD ANODIZE COATED VALVE WITH A SHARP METERING EDGE COMPRISING, FORMING A BLANK OF METAL WITH FIRST AND SECOND SURFACES THE PROJECTIONS OF WHICH WILL INTERSECT, A THIRD SURFACE CONNECTING SAID FIRST AND SECOND SURFACES AND SPACED INWARDLY FROM THE PROJECTED INTERSECTION OF SAID FIRST AND SECOND SURFACES, FORMING AN ADHERENT HARD ANODIZED COATING ON SAID FIRST, SECOND AND THIRD SURFACES AND THEREAFTER REMOVING A PORTION OF SAID COATING FROM SAID FIRST AND SECOND SURFACES UNTIL A SHARP EDGE IS FORMED BY THE COATING UPON SAID THIRD SURFACE AT THE INTERSECTION OF THE PLANES OF THE COATINGS ON SAID FIRST AND SECOND SURFACES. 